Variable electric resistance device



June 10, 1941. MQRQSS 2,244,958

VARIABLE'ELECTRIC RESISTANCE DEVICE 1 Filed Feb. 1, 1959 I? 52 71 71 76 J 70 l A 72 {I m 75 INVENTOR 7 69 75 fiagge E. 110105.:

' kl. ATTORNEY Patented June 10, 194i UNITED STATES PATENT OFFICE VARIABLE ELECTRIC RESISTANCE DEVICE Georgelllorosalaeksen Heights. N.Y..assignortoArthilrI.Ierreli,NewYork,N.!.

Application February 1, 1889, Serial No. 254,064

scum.

This invention relates to variable electric resistance devices or the type having a contact element movable on a resistance element for the purpose of varying the elective resistance of the device, and more particularly devices oi this type which are suitable ior automatic actuation.

In sensitive variable resistance devices such as are employed in controlling the current flowing in a circuit in an indicating or messurim instrument or the like, as for example. gauges tor measuring manifold, gasoline or oil pressum, it is desirable that the contact element and the resistsnce element be relatively movable tor varying the resistance, without substantial friction between these members. nirthermore, it is deairable that the contact element be maintained alainst the resistance element with sufllcient contact pressure to prevent sparking and to maintain a low contact resistance. It is further desirable, especially where the available actuating pressure is low, that the device shall be oi such construction as to be readily operable by relatively small iorces.-

According to the present invention, a resistance I element of suitable construction, as for example,

a wire wound resistance, a carbonaceous memher, or the equivalent, is provided. A contact elementisprovidedlorestablishlngsnadiustable contact with the resistance element. Actuating means. which in the present illustrative example, may be a fluid-pressure operated mechanism, is operatively connected to the contact element for moving relatively to the resistance element for the purpose of 7 8 the eflective resistance 0! the latter. The contact element is maintained in contact with the resistance element by resilient means which preferably also serve to resiliently oppose the action oi the actuating means whereby to return the contact element to its initial position upon discontinuance or diminution of the actuating iorce.

An object or the present invention is the provision o! avariable resistance device of the type described, including a resistance element and a contact element relatively movable tor the pinpose o! varying the eiiective resistance oi the resistance element, in which devbe the storesaid relative movement is eilected without undue me: object oi the invention is the provision at a variable resistance device 0! the character described wherein thecontact element and resistsnce element are relatively movable without undue friction, but suiilcient slip is provided to u maintain the surfaces of the contacting elements in clean condition.

Another object of the invention is the provision of a variable resistance device wherein the contact element is actuated in accordance with fluid pressure, the existence or extent of which it is desired to measure or employ in controlling the current in an electric circuit.

Still another object of the invention is the provision of a variable resistance of the type having a movable contact element adapted for automatic actuation to vary the effective resistance of the device wherein the device is capable of exerting a force opposing the action of the actuating means, which force varies according to the displacement of the contact element.

Still another object of the invention is the provision of a variable resistance device which is simple and rugged in construction, which is eilective and accurate in operation and which is generally suitable for the purposes desired.

Various other ieatures and advantages oi the invenflon will be apparent from the following particular description and from an inspection of the drawing.

Although the novel features which are believed to be characteristic or this invention will be particularly pointed out in the claims appended hereto. the invention itseli. as to its objects and advantages, and the manner in which it may be carried out, may be better understood by relerring to the iollowing description taken in connection with tin accompanying drawing forming a part hereol, in which Fig. l is a side elevational view or one iorm oi variable resistance device constructed in accordance with the invention;

Fig. 2 is an end elevational view or the device shown in Hg. 1;

Fig. '8 is a side elevational view 01 a second embodiment of the invention and illustrating particularly a variable resistance device having an adjustable resistance element;

Pig. 4 is a transverse cross-sectional view taken alongline Hot Fig.3:

Pig. 6 is a top plan view or a third embodiment of the invention and illustrating particularly a variable resistance device having a plurality of resistance elements and contact elements adapted to be operated as a unit;

l'lg. 6 is a side elevational view of the device ill utrated, in 1'18. 5;

Fig. 'l is a side elevational view 01 still another embodiment or the invention and illustrating particularly another form of multiple variable resistance device; and

Fig. 8 is a. fragmentary side elevational view of still another embodiment of the invention.

For the purposes of illustration, the present invention is disclosed in connection with several forms of variable resistance devices suitable for use in gauges for indicating fluid pressure, such as the manifold, gasoline or oil pressm'e of an internal combustion engine, such as commonly employed in aircraft, automobiics and the like, but it will be understood that the invention is capable application to other uses. It will also be understood that, in certain cases, the desired relative movement between the contact element and resistance element in response to an actuating or impulse :orce can be eflected in other ways than by the fluid-pressure responsive mechanism herein disclosed.

Referring now particularly to the embodiment of the invention illustrated in Figs. 1 and 2, the variable resistance device comprises a. resistance element I which may be wire wound as illustrated, or or any other suitable construction, and

which, for the purposes of illustration, comprises 0 a base or support 3 having a resistance wire 3 wound thereon and provided with leads 4 and 5 for connection to an electric circuit. The resistance element I is suitably secured, as by screws 8, to upstanding posts 8, 9 and I 0 of a frame or base I.

A contact element or member H is mounted in eiectrical contact with the resistance element I 811%.: preferably comprises a conductive member of nrcuate shape and sufficient rigidity to resist substantial distortion in operation. The contact element II is suitably connected, as by a pivot I8, to a suitable actuating means or device I! which, in the present example, comprises a pressure responsive diaphragm 20,, the interior of which is connected by a conduit I8 to the source of fluid pressure which is employed to effect the desired movement of the contact II, The controlling force of the actuating means or device is ei'fective through a predetermined path of movement.

The contact element H is provided with a lead I9 for connection to an electric circuit.

contact element II resiliently maintained in contact with the resistance element i by a pressure element I2 and is operative to rock on the resistance element I under the influence Of the actuating element it". The pressure element I2 preferably comprises a head It having a tapered point engaging the contact element ii a spring I4 urging the head l3 against the contact element, and means, such as a stud 5, for positioning the spring I4 relative to the frame 1. The member II is linked or positively joined at one of the ends thereof to the pressure element I2 or actuating means so that motion of the means is directly utilized in the operation of the device.

The operation of the variable resistance device is as follows:

The variable resistance device is connected in an electric circuit, the resistance of which is to be controlled, the lead IC, and either the lead 4 or the lead 5 being connected in the circuit. For the purpose of illustration, let it be assumed that the lead I! and the lead 4 are connected in a circult.

Assuming that there is no fluid pressure applied to the diaphragm 20, or that the minimum pressure is applied, the pressure element l 2 maintains the contact element H against the resistance elewhich is flexible, at least ment I, with the point of contact of these elements (hereinafter called the contact point") at or near the left hand end (as viewed in Fig. 1) of the resistance element I. When the fluid pressure in the diaphragm is increased, the latter expands and causes the contact element II to rock on the resistance element I and the contact point therefore is shifted to the right (as viewed in Fig. 1), thus increasing the resistance between the leads 4 and I3, and thereby increasing the effective resistance of the variable resistance device.

The distance between the point of application of pressure by the pressure element I2, contact point I I, and the point at which the actuating element I1 is connected to the contact element II may be suitably adjusted for providing the desired leverage for actuating the contact element II. If desired, the pressure of the element I! may be such as to permit a slight slippage of the contact element II on the resistance element I when the former is rocked, thereby to burnish the contacting surfaces and to maintain a uniform, low, contact resistance.

It will be noted that the pressure element I! not only maintains the contact element II against the resistance element I but also opposes the rocking of the contact element in response to the force exerted by the actuating device II. As the contact element I l is rocked, it compresses the spring I4 and thereby increases the resistance thereof, Moreover, owing to the movement of the contact point to the right, the lever arm constituted by the portion of the contact element II between the contact point and the pressure element l2 becomes longer and the lever arm formed by the portion of the contact element ll between the contact point and the actuating device I'I becomesshorter. Thus, the opposition offered by the pressure spring increases for this reason also.v It will be apparent from the foregoing that the characteristics of the opposing force presented by the pressure device can be selected as desired, by suitable construction or adjustment. of the several members.

Referrin now to Figs. 3 and 4, there is illustrated another embodiment of the invention, in which the variable resistance device comprises a resistance element which is adjustable whereby the characteristics 01' the device can be readily adjusted.

The variable resistance device comprises a resistance element having a base or support 33 at the portion carrying the conductive material. In the present case a wire wound resistance element is illustrated which has terminal lead; 26 and 21. The resistance element 25 is suitably secured to a frame 3| having upstanding posts 32 supporting a top member 30.

The resistance element is secured to the top member as by rivets 29 and an insulating member 33 is interposed between the resistance element 25 and the top member 30. One or more adjusting screws 34, 34 are threaded through the top member 30 and engage the insulating member 33 whereby the shape of the conducting portion of the resistance element can be varied. It will be understood that the base 28 of the resistance element 25 may be slotted at one of the rivets 29 as indicated in the drawing or may be otherwise constructed to permit adjustment by the adjusting screws 34, 34.

A contact element 35, which in the present embodiment is a straight member, is connected to an actuating element 4. which may be generally similar to the actuating element i1 previously described. The contact element It is resiliently and firmly maintained in contact with the resistance element by a pressure element ll which takes the iorm of an elongated leai spring rigidly secured at one end to the irame If and having an upturned end portion 31 engaging the free end of the contact element 35.

A terminal lead ll is connected to the contact element 36 and the connections to an electrical circuit can be made in a manner generally similar to that above described.

In the embodiment of the invention illustrated in Figs. 3 and 4, the device operates generally similar to the device illustrated in Figs. 1 and 2, except that the rocking action of the'contact element 3! on resistance element fl is possible by the reason of the arcuate iorm oi the resistance element 25. It will be seen that the resistance characteristics of the variable resistance device can be adjusted by adjusting the shape 01 the resistance element II.

Referring now to Figs. 5 and 6, there is illustrated a third embodiment of the invention wherein a plurality of resistance elements and contact elements are provided, the contact elements being actuated by a single actuating element. I

In this form oi the device. two resistance elements 5 and a are provided, having respectively terminal leads I, ll and 48a, 41a. The resistance elements 4! and a may be of any suitable construction and in the present example, they are wire wound.

The resistance elements ll and a are mounted side by side on a irame I! having upstanding posts 49 to which the resistance elements are secured.

A pair of contact elements 50 and "a are arranged in contact with the resistance elements and 46a respectively, the contact elements II and 500 being connected preferably at their ends by cross bars 5i and 52. The cross bar 2 is connected pivotally to a pressure element I which may be generally similar to the pressure elements previously described.

The contact elements El and Ila are resiliently maintained in contact with their respective resistance elements 45 and "a by a pressure element 53 which may comprise a head 54 hearing against the cross bar ii, a spring II and means such as a stud 58 ior maintaining the spring I! in position relative to the frame 48. The resistance elements 45 and 45a preferably are insulated from each other in suitable manner as by constructing the bases 49 thereof from insulating material or by interposing insulating material (not shown) between those parts which are to be insulated. The contact elements I and "a are insulated irom each other by constructing the cross bars BI and 52 of insulating material or by interposing insulating material (not shown) between them.

The contact elements and "a are provided with flexible terminal leads i1 and lid.

The resistance elements 45 and "a and their respective contact elements 50 and "a may be connected in separate circuits and the variable resistance device thus can be employed to vary the resistance oi these separate circuits in accordance with fluid pressure, the existence or extent of which it is desired to indicate or measure. The two resistance elements 45 and a may, if desired, have different resistance characteristics whereby the resistances oi the two circuits to be varied will vary dissimilar Referring now to Figure 7, there is illustrated another form oi multiple variable resistance device capable of controlling the resistance in two circuits simultaneously in accordance with the variation in a single fluid pressure.

The variable resistance device comprises a resistance element 65 which may be of any suitable construction and which has terminal leads 8' and 61 at each end and a third terminal lead I intermediate of the ends oi the resistance element, providing, in eiiect, two independent resistances.

The resistance element 05 is mounted on a irame I having upstanding posts I! to which the resistance element is suitably secured.

Two contact elements Ii and lid, which are of arcuate, rigid construction, are mounted in position to contact the two sections oi the resistance elements 05 respectively. The contact elements H and lid are suitably connected to a pressure element 1. which may be similar to the pressure elements hereinbeiore described.

Each contact element II is resiliently maintained in engagement with the corresponding section of the resistance element 05 by a pressure element Ii which may be constituted by a leaf spring I2 suitably secured to the frame 69 and having an end portion 13 engaging the contact element Ii preierably adjacent its end. For the purpose of providing a compact construction, the leaf spring 12 may be rebent as illustrated in Fig. 'l. The contact elements 1i and Ho have suitable terminal leads l6 and 11, respectively.

The variable resistance device illustrated in Fig. 7 may be employed in a manner analogous to the construction above described and may be connected in a single electric circuit in which case connections may be made between the terminal lead 6' and the terminal lead II or between the terminal leads 61 and I1. Where the device is thus employed, it will be understood that the contact elements ll and Ha are insulated from each other. Ii desired, the contact elements may be electrically connected in which case the connections to the electric circuit are made at the terminal leads 66 and 01.

Where the variable resistance device is to be employed for controlling the resistance of two separate circuits, connections may be made between the terminal leads 6 and I8, and between the leads 61 and 11 or between the terminal lead 8 and leads I6 and H or in other ways which will occur to those skilled in the art.

Referring now to Fig. 8, there is illustrated a further iorm of variable resistance device wherein the contact element is securely fixed relatively to the resistance element.

In this form of the device a resistance element ll of suitable construction is provided which has terminal leads Ii and 82, the resistance element being provided with or secured to a suitable support II which may be of rigid construction or which may be firmly secured in any position of adjustment.

A contact element is of suitable flexible construction is firmly fixed at one end relative to the resistance element, as for example, by attachment to the base I3. The contact element is pivotally connected to an actuating element II which may be similar in construction to the above mentioned actuating elements.

In this iorm oi variable resistance device the variation in resistance is produced by the varying extent of contact between the contact element and the resistance element as the contact e is forced into or out of engagement with the element accordingly as the pressure asment moves the adjacent end of the con- M element. The contact element 84 preferably is of resilient construction so that it is resiliently laid in engagement with the resistance element II, to the extent determined by the position of the actuating element I1.

In this form of the invention the device is preferably connected in an electric circuit by connection to the terminal leads II and I2. However, if desired, a terminal lead 88 may be connected to the contact element 84 or the actuating element I! in which case the circuit connections are made at the terminal leads I. and 01.

It will be noted that in construction illustrated in Fig. 8 the spring contact element ll serves to oppose upward movement of the actuating element l1. Owing to the distorting of the spring and to the shortness oi the lever arm between the contact point and actuating element II, the opposition to the actuating force increases as the actuating element moves upwardly. This increase can be made very rapid, owing to the relatively large movement of the free end of the contact element II as compared to its eii'ective length.

While certain novel features of the invention have been disclosed herein, and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of'the invention.

What is claimed is:

l. A variable electric resistance device comprising a resistance element, a rockably positioned member making a movable contact intermediate its ends with the resistance element to vary the effective resistance of the device, actuating means, the force of which is effective through a predetermined path of movement,

means for connecting one end or the rock member and the actuating means so the member is positively directed thereby to cause slippage between the member and the resistance element, and resilient means for engaging the other end of the rock member to maintain the contact of the member with the resistance element.

2. A variable electric resistance device comprising a relatively flexible resistance element, means for mounting said resistance element to provide the same with a definite curved surface, a rockably positioned member making a movable contact intermediate its ends with the curved surface of the resistance element to vary the eflective resistance of the device, actuating means for the device, means connecting said actuating means and one end of the rock member to directly utilize the movement of the actuating means to operate the device, means for yieldingly engaging the other end of the rock member to maintain the contact of the member with the element, and means by which the curvature of the flexible resistance element may be varied.

3. A variable electric resistance device comprising a plurality of resistance elements, a rockably positioned member making a movable contact intermediate its ends for each of the elements to vary the eii'ective resistance thereof, a common actuating means, the force of which is ei'lective through a predetermined path of movement, means for Joining said actuating means and one end of each of the rock members so the respective members are positively directed by the movement of the actuating means to cause slippage between each of the members and its associated resistance element, and yielding means for engaging the other end of each of the rock members to maintain the contacts thereof with the respective resistance elements.

GEORGE B. MOROSS. 

